Circuit breaker trip unit assembly



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CIRCUIT BREAKER TRIP UNIT ASSEMBLY Filed June 21, 1965 9 Sheets-Sheet 1Q INVENTORE y 9, 1967 A. STROBEL :ETAL 3,319,195

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CIRCUIT BREAKER TRIP UNIT ASSEMBLY Filed June 21, 1965 9 Sheets-Sheet 4INVENTORS 4165 67 $708t2 May 9, 1967 Al STROBEL ETAL 1 CIRCUIT BREAKERTRIP UNiT ASSEMBLY Filed June 21, 1965 9 Sheets-Sheet 5 y 19 7 A.STROBEL ETAL 3,319,195

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CIRCUIT BREAKER TRIP UNIT ASSEMBLY Filed June 21, 1965 9 SheetsSheet 9United States Patent vania Filed June 21, 1965, Ser. No. 465,313 15Claims. (Cl. 335-36) Our invention relates to molded case circuitbreakers in general, and more particularly to an improved trip unitassembly therefor which provides increased ease of manufacture,reliability of operation and calibration adjustment.

Automatic circuit breakers are usually provided with a trip unitincluding both a magnetic trip assembly, instantaneously responsive to asevere overload condition, and a thermal trip assembly, responsive to amoderate overload condition existing for a prolonged time interval. Theactuation of either the instantaneous or the delayed trip unitconventionally actuates a mechanism which causes a tripper bar to beurged into rotational movement, with such rotational movement serving tounlatch the general contact operating mechanism of the circuit breakerunit.

The instantaneous trip assembly conventionally includes a stationarymagnet member and a cooperating armature member. In order to achieverapid actuation responsive to a severe overload condition, it isdesirable that energization of the magnet be provided in such a mannerthat substantially all of the circuit breaker current Will serve toestablish the magnetic flux field. To insure reliable, safe and accurateoperation over extended periods of use, it is also necessary thatcalibration adjustments be proved for: (1) the initial position of thearmature; (2) the extent of armature travel required for tripping; (3)the biasing force to be overcome by the magnetic force; and (4)variation of the open-gap position in accordance with the particularcircuit parameters. In the past, the satisfaction of these variousrequirements has necessitated cumbersome and intricate trip unitstructures requiring excessive assembly time and cost.

It is a principal purpose of our invention .to provide an extremelysimplified trip unit assembly which provides these various functions inan efi'lcient manner while providing increased accessibility to thevarious members thereof, and specifically, the calibration adjustmentmeans.

Basically, the trip unit structure of our instant invention includes agenerally U-shaped magnet mounted such that its body portion ishorizontally located at the lower region of the overall trip unitassembly. The magnet includes generally upstanding arms havinghorizontally located pole faces at their end extremes. The cooperatingarmature member is horizontally located in a parallel plane above thepole faces. Normally the armature is separated from the pole faces by apredetermined gap distance, with such gap being rapidly closed upon theoccurrence of a predetermined excessive overload condition. The movementof the armature member is translated to the tripper bar by means of avertically extended actuating rod secured to the armature member, withthe rod having a transverse extension at one end thereof for engagementwith the tripper bar upon the downward movement of the armature. Theupper end of the actuating rod containing the trip unit actuatingextension is at an accessible region of the overall assembly, such thata calibration adjustment of the armature travel may be conveniently madeafter final assembly of the trip unit.

The mounting of the trip assembly is provided in an extremely simplifiedmanner by means of a unique mounting bracket serving a variety offunctions. The mounting bracket includes a generally L-shaped portionhaving a vertically extending rear planar portion and a forwardlyprojecting top portion. The forwardly projecting top portion ishorizontally disposed above the armature member. In one form of ourinvention, a sintered magnet is used having tapped openings within anenlarged cross-sectional area adjacent the pole faces. The tappedopenings receive screw members for securably mounting the magnet to themounting bracket and base support member. In another form of ourinvention, a cold rolled steel magnet is used, having a pair of inwardlyturned ear members, integral with the magnet and placed flush againstthe rear portion of the mounting bracket.

The armature member, which it will be recalled, is secured to theactuating rod, has the actuating rod extending through aligned openingsin the body portion of the magnet and the forwardly projecting portionof the bracket assembly. A vertically disposed planar surface of themounting bracket is located in juxtaposition with respect to a verticaledge of the armature and serves as a guide for movement thereof betweenits engaged and disengaged positions. Upward bias of the armaturetowards its disengaged position is provided by a spring member about thelower portion of the actuating rod. One end of the spring member bearsagainst the body portion of the magnet member and the other end urgesthe armature member upward. The bias force calibration may be providedby an adjustable nut, movable along the actuating rod and interposedbetween the upper end of the spring member and lower surface of thearmature. The lower surface of the forwardly projecting bracket supportportion advantageously serves as a positive stop for such upwardmovement, there-by facilitating the sub-assembly location of thearmature member.

It is also desirable that an externally accessible calibration member beprovided to adjust the magnetic trip characteristics in accordance withthe specific requirements of the circuit to be protected, as well as tocompensate for wear of the operating components. This externalcalibration is conveniently coupled to the magnet trip unit of ourinvention by the provision of an additional extension member along theactuating rod. This member is also movable along the actuating rod toprovide an initial calibration adjustment during manufacture.Advantageously, the external calibration unit is coupled to the tripunit such that the upper surface of the forwardly projecting supportbracket provides a reference surface.

Another extremely advantageous aspect of our invention relates to themanner in which the magnetic trip assembly is associated with, andelectrically connected to, the current carrying members of the circuitbreaker. Specifically, energization of the magnetic circuit is typicallyprovided by a current carrying strap passing therethrough such that theflux field generated thereby is coupled to the magnetic members. Theprior art magnetic trip assembly structures have typically necessitateda plurality of connecting points whereas the current carrying terminalstrap, or elements in electrical conductivity relationship therewith,were connected to the magnetic trip assembly. This arrangement tends topromote the astablishment of a parallel current path through themagnetic trip assembly. Such parallel current paths disadvantageouslydivert a portion of the current from its magnetizing function, therebyrequiring magnetic members of increased size, complexity and cost toprovide the necessary tripping forces response to the predeterminedoverload conditions. Further, the current flow through the magnetic tripassembly has in the past tended to cause welding of the armature to thecooperating pole faces of the magnet, thereby adversely affecting futurereliability of operation. These problems have in the past necessitatedthe additional expense and bothersome assembly procedure of includinginsulative members intermediate the current carrying elements of thecircuit breaker and the magnetic trip assembly. Our inventionadvantageously avoids these problems by requiring only a single point ofinterconnection between the magnetic trip assembly and those portions ofthe overall trip unit which are electrically connected to the currentcarrying path. The provision of such a single point connection preventsthe establishment of a parallel current path through the magnetic tripassembly. Advantageously, this single Point connection also serves tosecura-bly mount the thermal trip unit to our novel mounting bracket toprovide a combined magnetic and thermal trip unit of increasedsimplicity of structure and ease of fabrication.

Thus, it is seen that the L-shaped bracket of the instant inventionserves a variety of functions which, in addition to mounting themagnetic and armature of the trip unit base, serves as a positive stopfor the upward movement of the armature; guides the vertical movement ofthe armature during its travel; acts as a reference for the externallyaccessible magnet trip calibration means; and serves to mount thethermal trip in a manner avoiding a parallel current path through themagnetic trip.

It is therefore a primary object of our invention to provide asimplified magnetic trip unit assembly.

A further object of our invention is to provide a magnetic trip unitassembly wherein the operating components thereof may be simplyfabricated and assembled.

Another object of our invention is to provide a magnetic trip assemblyfor use in conjunction with a circuit breaker mechanism, which isconstructed to provide increased accessibility to the variouscalibration adjustments thereof.

An additional objects of our invention is to provide a circuit breakermagnetic trip unit assembly, including a novel mounting bracket servinga variety of functions.

Still a further object of our invention is to provide such a trip unitassembly where the mounting bracket serves as a guide for the armatureopen gap position, the path of armature movement, as well as thetripping characteristic calibration adjustment means.

Still another object of our invention is to provide a circuit breakermagnetic trip unit assembly wherein the electrical interconnectionbetween the current carrying members and the magnetic trip unit portionthereof is limited to a single point, thereby preventing theestablishment of parallel current paths within the magnetic trip unit.

Still an additional object of our invention is to provide a magnetictrip unit assembly which includes a generally U-shaped magnetic memberwith the arms thereof projecting upward for cooperation with ahorizontally disposed armature, such that actuation of themagneticcircuit moves the armature downward into engagement with themagnetic pole faces, with such downward armature movement being coupledto the circuit breaker tripper bar via an actuating rod secured to thearmature member and upwardly extending therefrom.

These, as well as other objects of our invention, shall become readilyapparent after reading the following description and the accompanyingdrawings, in which:

FIGURE 1 is a perspective view of a three-phase molded case circuitbreaker construction, which may be used in the practice of the instantinvention, and wherein the cover is removed to reveal the internalmechanism thereof;

FIGURE 2 is a plan view of the circuit breaker unit shown in FIGURE 1,with the cover replaced and partially cut away;

FIGURE 3 is a longitudinal cross-sectional view taken through the centerphase and along the arrows 3-3, as shown in FIGURE 2;

FIGURE 4 is a cross-sectional view along the lines 44 of FIGURE 1 andshowing one form of the trip unit assembly, in accordance with ourinvention;

FIGURE 5 is a top view of FIGURE 4 showing the trip unit assembly, andpartially broken away in crosssection;

FIGURE 6 is a cross-sectional view along the lines 66 of FIGURE 4,looking in a direction of the arrows and showing further details of thetrip unit assembly, with the magnetic trip portion thereof shown in thenontripped condition;

FIGURE 7 corresponds to FIGURE 6, but shows the magnetic trip unit inthe actuated or tripped condition;

FIGURE 8 is a perspective view of the trip unit assembly of FIGURES 4-7;and

FIGURE 9 is an exploded perspective view of the magnetic trip unit inconjunction with the trip unit assembly and calibration adjustmentbutton, and FIGURE 9A explodes the magnetic trip portion of the tripunit assembly.

FIGURE 10 is a perspective view of another form of trip unit assembly inaccordance with our invention, which has a somewhat modified magnetictrip portion; and

FIGURE 11 is an exploded perspective view of the modified magnetic tripportion thereof.

Now referring to the figures: circuit breaker 10 where in our inventionis incorporated is typically shown as a commercially availablethree-phase molded case unit. It should be naturally understood that thenovel concepts of our invention may be incorporated in numerous otherframe sizes and types, with this embodiment being merely forillustrative purposes. The unit is assembled within a housing comprisingmolded base 11, separated into compartments 12, 13 and '14,respectively, for locating the operating members of each 'of the phases.The adjacent compartments are separated by housing walls 15 and 16. Maincover assembly 17 and end covers 18 similarly include barriers formaintaining the longitudinally extending compartments of the housing,with end shields 19 being located at the line and load ends of thecircuit breaker 10.

The current carrying members of all three phases are identical so thatfor the sake of brevity only one of the sets of elements, such as thecenter phase as shown in FIGURE 3, will be described. The current pathbetween the line terminal strap 20 and load terminal strap 21 pro ceedsfrom stationary contacts 22 and 23 to movable contacts 24 and 25 carriedby contact arms 26 and 27 through flexible braids 28, contact carrierstrap 29 and trip unit strap 102.

Since circuit breaker 10 is of a relatively high current carryingcapacity, contacts 22-24 function as arcing contacts and are properlysituated to move into engagement and disengagement within the openingdefined by circuit breaker arc chute assembly 31. The arcing contacts22-24 are shown parallelled by two seats of main contacts 23-25. Themain movable contacts 25 are each mounted to individual contact arms 27,each connected by an individual section of braid 28 to contact carrierstrap 29, while cooperating stationary contacts 23 are mounted to lineterminal strap 20. The movable arcing contact 24 is similarly mounted toits contact arm 26, which is connected by a braid section 28 to thestrap 29. Its c0- operating stationary contact 22 is also mounted toline terminal strap 20. The contact arms 26-27-26 of each phase are, inturn, pivotally mounted by rod 36 to contact carrier 35.

The movable contact arm mounting may include individual adjusting studs60 to establish the open gap circuit position of contacts 24-25 relativeto stationary contacts 22-23 as shown in the open position of FIGURE 3;as well as a contact pressure adjustment means shown as 71; as is thesubject of copending U.S. patent application Ser. No. 430,549 filed Feb.5, 19 65, in the name of Carl E. Gryctko and entitled, Circuit BreakerContact Mounting, now U.S. Patent No. 3,268,702..

Circuit breaker 10 also includes an automatic tripping mechanism and aquick make-break-toggle operating mechanism 32. Operating mechanism 32is connected to the contacts of all three phasees by means of atransverse insulating tiebar 33, with U-shaped straps 34 connecting therespective contact carriers 35 to the common tiebar 33. Carrier 35 ispivotally mounted at 46- to suitable bearings in the operating mechanismframe 47. Mounting frame 47 includes ears 84 which receive screw members49 for securement to circuit breaker base embossment 50.

The center phase carrier 35 is connected at its pivot rod 36 to thelower of the operating mechanism toggle linkage 37-38, with the togglelinks joined at knee 39. Knee 39 includes a pivotally mounted platemember 40- to which the circuit breaker operating springs, shown as apair 41-41, are connected at one end 42-42 thereof. The other ends43-43" are located in suitable apertures with the operating handle frame45, such that the operating springs 45-45 are in overcenter relationshipwith respect to toggle linkage 37-38. The lower end of handle framemember 45 is pivotally mounted to bosses 83 of operating mechanism frame47. Operating handle 80 is mounted to upstanding posts 81 of framemember 45.

The operating mechanism 32 also includes a cradle carried lat-ch tip 51for engagement with latching bracket extension '52 of the trip assembly100. A coupling member generally shown as 52 interconnects latchingbracket extension 52 to the tripper bar 53 of the trip unit assembly soas to effect tripping disengagement of latched members 51-52 uponcounter-clockwise movement of tripper bar 53. Such counter-clockwisemovement is effected by either the actuation of the instantaneous ormagnetic trip or the time-delayed or thermal trip units contained intrip unit assembly 100.

The trip unit assembly 100 includes a terminal strap 102 for each of thephases. Terminal straps 102 include apertures 104 at one end thereof tomate with cooperating aperture 106 of the load terminal strap 21 forelectric-a1 and mechanical securement thereto. The opposite end ofterminal strap 102 includes aperture :108 which similarly mates withcooperating aperture 110 of the contact carrier strap 29. Bolt means 112extend through cooperating apertures 104, 106 at the load end of thecircuit breaker frame, with similar bolt means 114 extending throughcooperating apertures 108, 110 for mounting each of the terminal straps102 of the trip unit assembly 100 to their respective load terminalstraps 21 and contact carrier straps 29.

The magnetic trip assembly, which is the subject of the instantinvention and is generally shown as 250, includes an actuating rod 56having a trip unit actuating extension 57 which moves down intoengagement with tripper bar extension member '58. The trip unitactuating extension 57 to the upper extreme of actuating rod 56 ispreferably of an external knurled configuration to facilitate adjustmentthereof, during the initial calibration procedure. Extension 57 is alsoof a sufiicient diameter to extend over a substantial portion of itscooperating tripper bar bracket 58. This advantageously avoids the useof a fork-type tripping bracket and the cumbersome assembly techniquesassociated therewith, as is required in some prior art structures.Furthermore, this design eliminates pole-to-pole misalignment problemsbetween armature trip rod and tripping bracket that are commonly presentwhen fork type brackets are used.

The time-delayed trip unit assembly includes an elongated bimetallicmember 54 which will deflect towards the left, as shown in FIGURE 3,into engagement with tripper bar adjustment screw 55 upon the occurrenceof moderate overload conditions for a predetermined interval of time.

With respect to the specific details of the magnetic trip unit assemblyof the instant invention, reference is first made to FIGURES 4-9, whichshow one form thereof.

The magnetic trip unit assembly 250 includes a cooperating magnet member101 and armature 103. Magnet member 101, which may be of the sinteredvariety, has a generally U-shaped configuration which includes a bodyportion 105 disposed generally horizontally and mounted at the lowermostregion of the overall trip unit assembly 100. The ends of body portion105 include upstanding space-separated arms 107, 109, respectively,having horizontally disposed pole faces 111, 113, respectively, at theiruppermost extremes. The upper portions of the arms 10-7, 109 includeenlarged cross-section areas 116, 118, respectively, having tappedopening 157. These openings are in alignment with openings 159 of themounting bracket 150, 206 of the terminal shunt bracket 204, as well ascooperating opening (not shown) of the base support 200, for receivingmounting screws 155.

The armature member '103 is horizontally positioned intermediate theplane of pole faces 111, 113 and the bottom surface 161 of forwardlyprojecting extension 154 of the mounting bracket 150. In its non-engagedcondition, as shown in FIGURE 6, the armature member 103 is separatedfrom the pole faces 111, 1 13 by an airgap separation of predeterminedcalibrated extent, as shown by d. Upon sufiicient magnetizing flux thearmature member 103 is downwardly drawn towards cooperating pole faces111, 113 as shown in FIGURE 7.

The mounting of the armature member for travel between its engaged andnon-engaged positions is provided in the following manner. Actuating rodmember 56, which extends through cooperating aligned apertures 163 ofthe mounting bracket top portion, 165 of the thermal trip unit assemblyand 167 of the magnetic member body portion 105, is secured to thearmature member at 170. A biasing spring 172 is positioned about thelower portion of actuating rod 56 with the bottom end 173 thereofbearing against the upper surface of magnetic member body portion 105and the top end 174 bearing against a calibration adjustment nut member175. Thus, the armature member will be located with the bias spring 172serving to urge the armature upwards to its disengaged position. Toguide the movement of armature 103 between its engaged and disengagedconditions, the rearmost edge 164 thereof is in juxtaposition to forwardsurface of the mounting bracket forwardly turned portion 152, as bestseen in FIGURES 8 and 9. It should be noted at this point that the lowersurface 161 of the forwardly projecting bracket portion 154 will be inthe path of upward travel of the armature member 103 and serve as apositive step to limit such upward movement. This feature isparticularly advantageous during the sub-assembly fabrication of thecircuit breaker trip unit.

An armature gap calibration means, generally shown as 185, is provided.This adjustment means which is the subject of copending U.S. patentapplication entitled Circuit Breaker Instantaneous Trip Adjustment, Ser.No. 465,305, filed June 21, 1965, and assigned to the assignee of theinstant invention, includes a mounting bracket 187 having an externallyaccessible calibration button 189, for rotation of cam member 191. Thisrotational movement causes vertical translation of calibrationadjustment extension secured to the actuating rod 56 in accordance withthe cam surface 193 of rotatable cam 191. Such movement of the actuatingrod 56 naturally moves the armature member 103 a corresponding distanceto adjust the gap separation d. The armature gap calibration adjustmentmeans includes a lower pin member 197 which rests on upper surface 162of the mounting bracket forward projecting top portion 154. Thisadvantageously serves as a reference plane for the gap calibrationadjustment, as well as serving to position pin 197 against thecalibration adjust bias force provided from within member 189.

It should he noted at this point that the trip unit actuating extension57, the calibration adjustment extension 195 and armature bias pressurecalibration nut 175 are all threadedly maintained along actuating rod 56and are easily accessible subsequent to final assembly of the overalltrip unit assembly; as shown, for example, in FIG- URE 8. After thesecalibrated adjustments are made, the extension members 57, 195 and 175are properly secured in place along the actuating rod 56, as by solder.This is to be contrasted to the intricate adjustment structuresnecessitated by the prior art trip unit assemblies for calibrating thesevarious parameters.

The energization for the magnetic trip unit assembly is provided bycurrent carrying strap member 102 passing through the U-arins of magnetmember 101. Current carrying strap member 102 is connected to a thermalshunt 202 which in turn is thermally connected to the bimetallic :member54, as is more fully disclosed in copend ing US. patent applicationentitled, Circuit Breaker Trip Assembly With Increased Compensation forMisalignmerit, Ser. No. 465,304, filed June 21, 1965 and assigned to theassignee of the instant invention. The thermal trip unit includes amounting bracket 204 which has apertures 206 in alignment with apertures159 of the mounting bracket 150 and 157 of the magnet 101 for receivingscrews 155. The combined magnetic and thermal trip unit assemblies ofeach of the phases are mounted to a base support member 200 of theoverall trip unit assembly, as by mounting screws 212, which mate withapertures 210. Thermal shunt member 202 may typically be formed ofcopper laminates or other conductive material. Hence, this couldestablish a current path from the conductive strap 102 via terminalshunt member 202 and mounting bracket 204 of the time delay tripsubassembly to the main mounting bracket :member 150 and magnet member101. Should there be a current return, the possibility of such aparallel current path tends to lower the pull-in force of the magnet 101as well as subjecting the armature and magnet to the danger of welding.Our invention absolutely avoids this by the provision of only one pointof interconnection between the magnet trip unit and the current carryingmembers of the overall trip assembly, thereby avoiding the necessity ofincluding insulative members in the assembly.

Reference is now made to FIGS. 1'0 and 11 which sh w another form of ourinvention having a slightly modified magnetic trip assembly. To simplifythe comparison with the embodiment described above, components of likedesignations are indicated by the same numerals and those componentshaving a corresponding function are indicated by prime numerals. It isnoted that magnet member 101' is now formed of a uniform thickness ofmaterial, which may be, for example, cold rolled steel. Magnet members101 is of a general U-shaped configuration, including a central bodyportion 105', having upstanding arms 107', 109', with the pole faces111, 113' at the ends thereof. A pair of inwardly turned mounting ears116, 118' are provided, having tapped openings 157, which receivemounting screws 155. Mounting openings 157 are in alignment withcooperating openings 159 of the mounting bracket for securely mountingthe magnet member 101' to the mounting bracket 150'.

Mounting bracket 150' is similarly of a generally L- shapeconfiguration, having a generally vertically extending rear planarportion 185' and a forwardly projecting top portion 154' extending in agenerally horizontal direction. Rearwardly extending U-sections 152having openings 159' which mate with screw members 212' (and cooperatingopenings of the thermal shunt mounting bracket, not shown) provided forsecurably fixing the mounting bracket to the trip unit support member200.

It will be noted that in this embodiment of our invention the verticallyorientated planar surface 185' of the mounting bracket is injuxtaposition to the rear edge 164' of the armature and serves to guideits vertical movement; the bottom surface 161' of the forwardlyprojecting portion 154' of the mounting bracket serves asa positive stopfor the upward movement of the armature 103'; the

8 upper surface 162' of the mounting bracket forward extension serves asa reference for the externally accessible magnetic trip calibrationmeans, and likewise serves to mount the thermal trip in a manneravoiding a parallel current path through the magnetic trip.

It is accordingly seen that the instant invention provides a trip unitassembly of substantially increased simplicity of parts, ease ofmanufacture, increased reliability, as well as permitting increasedaccessibility to the variety of calibration adjustments associatedtherewith.

Although there have been described preferred embodiments of our novelinvention, many variations and modifications will now be apparent tothose skilled in the art. Therefore, this invention is to be limited,not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. A circuit breaker comprising at least one pair of cooperatingcontacts, contact operating means for moving said contacts between anengaged and disengaged position; latch mean cooperating with saidoperating means for maintaining said contacts in their engaged positionunder normal load conditions, a trip unit including current sensingmeans operatively responsive to the current flow through the circuit,and including means for releasing said latch means responsive topredetermined overload conditions, said current sensing means includinga magnetic trip assembly having cooperating magnet and armature members,said magnet member of a generally U- shaped configuration, includingspace-separated arms joined by a body portion, said body portiondisposed generally horizontally, and mounted at the lower region of saidtrip unit, with said arms vertically extending upwardly therefrom, theuppermost ex'u'emes of said arms including pole faces disposed in agenerally horizontal plane, vertically displaced upwards from said bodyportion, said armature member horizontally extending parallel to theplane of said pole faces, and bridging the space separation between thearms thereof, said armature member having a first position above saidpole faces, and separated therefrom by a predetermined gap with saidfirst position corresponding to the disengaged condition of the magnetictrip assembly, said armature having a second position, in contact withsaid pole faces, with said second position corresponding to the engagedcondition of the magnetic trip assembly, magnet energizing means formoving said armature downwardly between said first and second positionscorresponding to a predetermined overload condition, an actuating rodmounted to said armature, and including a first portion upwardlyextending therefrom in a generally vertical direction, a trip unitactuating extension mounted to said rod for movement therewithresponsive to downward movement of said armature towards its engagedcondition, means operatively connecting said actuating extension to saidcontact operating latch means, for release of said latch meansresponsive to downward movement of said actuating rod, including meansfor upwardly biasing said armature towards its first position, saidactuating rod including a second portion downwardly extending towardssaid magnet body portion, said biasing means including an elongatedspring about said actuating rod second portion, a first end of saidspring bearing against a surface of said magnet body portion, and asecond end of said spring bearing against a pressure adjustmentextension mounted to said actuating rod.

2. A circuit breaker comprising at least one pair of cooperatingcontacts, contact operating means for moving said contacts between anengaged and disengaged position; latch means cooperating with saidoperating means for maintaining said contacts in their engaged positionunder normal load conditions, a trip unit including current sensingmeans operatively responsive to the current flow through the circuit,and including means for releasing said latch means responsive topredetermined overload conditions, said current sensing means includinga magnetic trip assembly having cooperating magnet and armature members,said magnet member of a generally U- shaped configuration, includingspace-separated arms joined by a body portion, said body portiondisposed generally horizontally, and mounted at the lower region of saidtrip unit, with said arms vertically extending upwardly therefrom, theuppermost extremes of said arms including pole faces disposed in agenerally horizontal plane, vertically displaced upwards from said bodyportion, said armature member horizontally extending parallel to theplane of said pole faces, and bridging the space separation between thearms thereof, said armature member having a first position above saidpole faces, and separated therefrom by a predetermined gap with saidfirst position corresponding to the disengaged condition of the magnetictrip assembly, said armature having a second position, in Contact withsaid pole faces, with said second position corresponding to the engagedcondition of the magnetic trip assembly, magnet energizing means formoving said armature downwardly between said first and second positionscorresponding to a predetermined overload condition, an actuating rod,means rigidly connecting said actuating rod to said armature, saidactuating rod including a first portion upwardly extending therefrom ina generally vertical direction, a trip unit actuating extension mountedto said rod for movement therewith responsive to downward movement ofsaid armature towards its engaged condition, means operativelyconnecting said actuating extension to said contact operating latchmeans, for release of said latch means responsive to downward movementof said actuating rod, including means for adjusting said predeterminedgap separation including a gap adjustment extension mounted to saidactuating rod, and vertically displaceable by an externally accessiblemember such that said armature is vertically adjustable relative to saidpole faces,

3. A circuit breaker as set forth in claim 1, means for adjusting saidpredetermined gap separation including a gap adjustment extensionmounted to said actuating rod,

and vertically displaceable by an externally accessible member, suchthat said armature is vertically adjustable relative to said pole faces.

4. A circuit breaker as set forth in claim 3, wherein at least a portionof the length of said actuating rod is externally threaded, at least oneof said extensions formed of a member having an internal thread formating engagement with said rod threaded portion, .said membervertically movable along said rod for calibrated adjustment of itsrespective function.

5. A circuit breaker as set forth in claim 3, wherein said actuating rodincludes externally threaded portions, each of said extensions includingan internally threaded member, such that said extensions are verticallymovable along said rod threaded portions for calibrated adjustment ofthe trip unit release, armature bias force and open gap separation.

6. A circuit breaker as set forth in claim 5, wherein said trip unitincludes a support member, mounting means for mounting said magnetictrip assembly to said support member of said trip unit, said mountingmeans constructed to provide accessibility to said calibratedadjustment, whereby said magnetic trip assembly may be readilycalibrated when mounted to said trip assembly support member.

7. A circuit breaker comprising at least one pair of cooperatingcontacts, contact operating means for moving said contacts between anengaged and disengaged position, latch means cooperating with saidoperating means for maintaining said contacts in their engaged positionunder normal load conditions, a trip unit including current sensingmeans operatively responsive to the current flow through the circuit,and including means for releasing said latch means responsive topredetermined overload conditions, said current sensing means includinga magnetic trip assembly having cooperating magnet and armature members,said magnet member of a generally U-shaped configuration, includingspace-separated arms joined by a body portion, said body portiondisposed generally horizontally, and mounted at the lower region of saidtrip unit, with said arms vertically extending upwardly therefrom, theuppermost extremes of said arms including pole faces disposed in agenerally horizontal plane, vertically displaced upwards from said bodyportion, said armature member horizontally extending parallel to theplane of said pole faces, and bridging the space separation between thearms thereof, said armature member having a first position above saidpole faces, and separated therefrom by a predetermined gap, with saidfirst position corresponding to the disengaged condition of the magnetictrip assembly, said armature having a second position, in contact withsaid pole faces, with said second position corresponding to the engagedcondition of the magnetic trip assembly, magnet energizing means formoving said armature downwardly between said first and second positionscorresponding to a predetermined overload condition, an actuating rodmounted to said armature, and including a first portion upwardlyextending therefrom in a generally vertical direction, a trip unitactuating extension mounted to said rod for movement therewithresponsive to downward movement of said armature towards its engagedcondition, means operatively connecting said actuating extension to saidcontact operating latch means, for release of said latch meansresponsive to downward movement of said actuating rod, said trip unitincluding, a mounting bracket for mounting said magnetic trip assembly,said mounting bracket including a generally Vertically extending rearplanar portion communicating with a forwardly projecting top portion,said top portion extending in a generally horizontal direction, parallelto and above said armature member, said magnet member including mountingregions integrally formed therein, securing means for securably mountingsaid mounting regions to said mounting bracket rear portion,

8. A circuit breaker as set forth in claim 7, further including meansfor upwardly biasing said armature towards its first position, saidactuating rod including a second portion downwardly extending towardssaid magnet body portion, said biasing means including an elongatedspring about said actuating rod second portion, a first end of saidspring bearing against a surface of said magnet body portion, and asecond end of said spring bearing against a pressure adjustmentextension mounted to said actuating rod, said forwardly projecting topportion having an upper and lower surface, said lower surface in theupward path of travel of said armature, and serving as a positive stopmeans for the upward movement of said armature memher.

9. A circuit breaker as set forth in claim 7, wherein said forwardlyprojecting top portion has an upper and lower surface, said lowersurface is in the upward path of travel of said armature and serves as apositive stop means for the upward movement of said armature member.

10. A circuit breaker as set forth in claim 7, wherein said forwardlyprojecting top portion has an upper and lower surface, and furtherincluding means for adjusting said predetermined gap separationincluding a gap adjusted extension mounted to said actuating rod, andvertically displaceable by an externally accessible member, such thatsaid armature is vertically adjustable relative to said pole faces, saidgap separation adjustment means including a member in engagement withsaid top surface, such that said top surface provides a support guidefor said adjustment means.

11. A circuit breaker as set forth in claim 7, further including meansfor upwardly biasing said armature towards its first position, saidactuating rod including a second portion downwardly extending towardssaid magnet body portion, said biasing means including an elongatedspring about said actuating rod second portion, a first end of saidspring bearing against a surface of said magnet body portion, and asecond end of said spring bearing against a pressure adjustmentextension mounted to said actuating rod, means for adjusting saidpredetermined gap separation, including a gap adjustment extensionmounted to said actuating rod, and vertically displaceable by anexternally accessible member, such that said armature is verticallyadjustable relative to said pole faces, said forwardly projecting topportion having an upper and lower surface, said lower surface in theupward path of travel of said armature, and serving as a positive stopmeans for the upward movement of said armature member, said gapseparation adjustment means including a member in engagement with saidtop surface, such that said top surface provides a support guide forsaid adjustment means.

12. A circuit breaker as set forth in claim 7, wherein said armaturemember includes a generally vertically extending edge in juxtapositionto a vertically extending bracket portion, said vertically extendingbracket portion defining the path of movement of said armature memberedge corresponding to the movement of said armature between its firstand second positions, such that said last mentioned bracket portionprovides a guide for the armature travel.

13. A circuit breaker as set forth in claim 11, wherein said armaturemember includes a generally vertically extending edge in juxtapositionto a vertically extending bracket portion, said vertically extendingbracket portion defining the path of movement of said armature memberedge corresponding to the movement of said armature between its firstand second positions, such that said last mentioned bracket portionprovides a guide for the armature travel.

14. A circuit breaker comprising at least one pair of cooperatingcontacts, contact operating means for moving said contacts between anengaged and disengaged position, latch means cooperating with saidoperating means for maintaining said contacts in their engaged positionunder normal load conditions, a trip unit including current sensingmeans operatively responsive to the current fiow through the circuit,and including means for releasing said latch means responsive topredetermined overload conditions, said current sensing means includinga magnetic trip assembly having cooperating magnet and armature members,said magnet member of a generally U-shaped configuration, includingspace-separated arms joined by a body portion, said body portiondisposed generally horizontally, and mounted at the lower region of saidtrip unit, with said arms vertically extending upwardly therefrom, theuppermost extremes of said arms including pole faces disposed in agenerally horizontal plane, vertically displaced upwards from said bodyportion, said armature member horizontally extending parallel to the.plane of said pole faces, and bridging the space separation between thearms thereof, said armature member having a first position above saidpole faces, and

separated therefrom by a predetermined gap, with said first positioncorresponding to the disengaged condition of the magnetic trip assembly,said armature having a second position, in contact with said pole faces,with said second position corresponding to the engaged condition of themagnetic trip assembly, magnet energizing means for moving said armaturedownwardly between said first and second positions corresponding to apredetermined overload condition, an actuating rod mounted to saidarmature, and including a first portion upwardly extending therefrom ina generally vertical direction, a trip unit actuating extension mountedto said rod for movement therewith responsive to downward movement ofsaid armature towards its engaged condition, means operativelyconnecting said actuating extension to said contact operating latchmeans, for release of said latch means responsive to downward movementof said actuating rod, said trip unit including a mounting bracket formounting said magnetic trip assembly, said mounting bracket including agenerally vertically extending rear planar portion communicating with aforwardly projecting top portion, said top portion extending in agenerally horizontal direction, parallel to and above said armaturemember, said magnet member including mounting regions integrally formedtherein, securing means for securably mounting to said mounting regionsto said mounting bracket rear portion, said magnet energizing meansbeing a current carrying terminal strap passing through the U-arms ofsaid magnet member, a thermal shunt meansconnected to said terminalstrap at a first end thereof, and connected to said mounting bracket ata second end thereof, said terminal shunt providing the sole connectionbetween the current carrying terminal strap and the magnetic tripassembly, whereby a parallel current path in the trip unit assembly isavoided.

15. A circuit breaker as set forth in claim 14, further including athermally actuated tripping element mounted to said second end of saidthermal shunt, an intermediate bracket member secured to said thermallyactuated element and thermal shunt at a central portion thereof, andmounted to said mounting bracket at end extremes thereof, such that saidthermal trip element is mounted to said mounting bracket.

References Cited by the Examiner UNITED STATES PATENTS 2,294,838 9/1942Dorfman 200-88 3,097,277 7/1963 Wingard 20088 3,206,576 9/1965 Michetti200- References Cited by the Applicant UNITED STATES PATENTS 2,047,7397/1936 Lingal.

BERNARD A, GILHEANY, Primary Examiner.

H. E. SPRINGBORN, Assistant Examiner.

2. A CIRCUIT BREAKER COMPRISING AT LEAST ONE PAIR OF COOPERATINGCONTACTS, CONTACT OPERATING MEANS FOR MOVING SAID CONTACTS BETWEEN ANENGAGED AND DISENGAGED POSITION; LATCH MEANS COOPERATING WITH SAIDOPERATING MEANS FOR MAINTAINING SAID CONTACTS IN THEIR ENGAGED POSITIONUNDER NORMAL LOAD CONDITIONS, A TRIP UNIT INCLUDING CURRENT SENSINGMEANS OPERATIVELY RESPONSIVE TO THE CURRENT FLOW THROUGH THE CIRCUIT,AND INCLUDING MEANS FOR RELEASING SAID LATCH MEANS RESPONSIVE TOPREDETERMINED OVERLOAD CONDITIONS, SAID CURRENT SENSING MEANS INCLUDINGA MAGNETIC TRIP ASSEMBLY HAVING COOPERATING MAGNET AND ARMATURE MEMBERS,SAID MAGNET MEMBER OF A GENERALLY USHAPED CONFIGURATION, INCLUDINGSPACE-SEPARATED ARMS JOINED BY A BODY PORTION, SAID BODY PORTIONDISPOSED GENERALLY HORIZONTALLY, AND MOUNTED AT THE LOWER REGION OF SAIDTRIP UNIT, WITH SAID ARMS VERTICALLY EXTENDING UPWARDLY THEREFROM, THEUPPERMOST EXTREMES OF SAID ARMS INCLUDING POLE FACES DISPOSED IN AGENERALLY HORIZONTAL PLANE, VERTICALLY DISPLACED UPWARD FROM SAID BODYPORTION, SAID ARMATURE MEMBER HORIZONTALLY EXTENDING PARALLEL TO THEPLANE OF SAID POLE FACES, AND BRIDGING THE SPACE SEPARATION BETWEEN THEARMS THEREOF, SAID ARMATURE MEMBER HAVING A FIRST POSITION ABOVE SAIDPOLE FACES, AND SEPARATED THEREFROM BY A PREDETERMINED GAP WITH SAIDFIRST POSITION CORRESPONDING TO THE DISENGAGED CONDITION OF THE MAGNETICTRIP ASSEMBLY, SAID ARMATURE HAVING A SECOND POSITION, IN CONTACT WITHSAID POLE FACES, WITH SAID SECOND POSITION CORRESPONDING TO THE ENGAGEDCONDITION OF THE MAGNETIC TRIP ASSEMBLY, MAGNET ENERGIZING MEANS FORMOVING SAID ARMATURE DOWNWARDLY BETWEEN SAID FIRST AND SECOND POSITIONSCORRESPONDING TO A PREDETERMINED OVERLOAD CONDITION, AN ACTUATING ROD,MEANS RIGIDLY CONNECTING SAID ACTUATING ROD TO SAID ARMATURE, SAIDACTUATING ROD INCLUDING A FIRST PORTION UPWARDLY EXTENDING THEREFROM INA GENERALLY VERTICAL DIRECTION, A TRIP UNIT ACTUATING EXTENSION MOUNTEDTO SAID ROD FOR MOVEMENT THEREWITH RESPONSIVE TO DOWNWARD MOVEMENT OFSAID ARMATURE TOWARDS ITS ENGAGED CONDITION, MEANS OPERATIVELYCONNECTING SAID ACTUATING EXTENSION TO SAID CONTACT OPERATING LATCHMEANS, FOR RELEASE OF SAID LATCH MEANS RESPONSIVE TO DOWNWARD MOVEMENTOF SAID ACTUATING ROD, INCLUDING MEANS FOR ADJUSTING SAID PREDETERMINEDGAP SEPARATION INCLUDING A GAP ADJUSTMENT EXTENSION MOUNTED TO SAIDACTUATING ROD, AND VERTICALLY DISPLACEABLE BY AN EXTERNALLY ACCESSIBLEMEMBER SUCH THAT SAID ARMATURE IS VERTICALLY ADJUSTABLE RELATIVE TO SAIDPOLE FACES.